CVE-2025-10018: Quick.cms Language Editor XSS Vulnerability

CVE-2025-10018 Overview

CVE-2025-10018 is a stored Cross-Site Scripting (XSS) vulnerability in Opensolution Quick.cms version 6.8. The flaw resides in the language editor functionality (languages), where input is not properly sanitized before being rendered. An authenticated attacker with administrative privileges can inject arbitrary HTML and JavaScript that executes on every page of the affected website. By default, administrator users are not permitted to add JavaScript to the website, so this flaw bypasses that intended restriction. The vendor was notified early but did not respond with vulnerability details or a vulnerable version range. Only version 6.8 was tested and confirmed vulnerable; other versions may also be affected.

Critical Impact
Authenticated administrators can inject persistent JavaScript into every rendered page, enabling session theft, defacement, and client-side attacks against other administrators and site visitors.

Affected Products

Opensolution Quick.cms 6.8 (confirmed)
Other Quick.cms versions (untested, potentially affected)
Deployments exposing the admin language editor to multi-user administrative access

Discovery Timeline

2025-11-14 - CVE-2025-10018 published to the National Vulnerability Database (NVD)
2026-10-07 - Last updated in NVD database

Technical Details for CVE-2025-10018

Vulnerability Analysis

The vulnerability is a stored XSS flaw [CWE-79] in the Quick.cms administrative language editor. Language strings edited through the languages interface are stored and later rendered without proper output encoding or input sanitization. Because language strings are referenced across the application, injected payloads execute on every page that references the modified string. The impact includes session hijacking of other administrators, forced actions through CSRF chaining, credential harvesting via injected forms, and client-side redirection to attacker-controlled infrastructure. The flaw also bypasses the application's default control that prevents administrators from inserting JavaScript into site content.

Root Cause

The root cause is improper neutralization of user-controlled input during web page generation. The language editor accepts HTML and script content from privileged users without applying contextual output encoding or an allowlist filter. Although administrators are a trusted role, the application explicitly restricts JavaScript insertion elsewhere, meaning the language editor represents an unintended privilege expansion beyond the documented role boundary.

Attack Vector

Exploitation requires an authenticated session with high administrative privileges (PR:H) and some user interaction (UI:P) by a victim who views an affected page. The attacker modifies a language string through the admin panel and inserts an HTML or JavaScript payload. The payload is persisted in the language data store and executed whenever a user, including other administrators, loads a page that renders the affected string. Secondary impact extends beyond the vulnerable component to any content rendered using the compromised language resource.

No verified public proof-of-concept code is available. For technical analysis, refer to the CERT.pl CVE-2025-9982 Analysis and OpenSolution CMS Quick Documentation.

Detection Methods for CVE-2025-10018

Indicators of Compromise

Unexpected <script>, <iframe>, or event-handler attributes (for example, onerror, onload) stored in language files or language database tables
Outbound requests from browser sessions to unfamiliar domains immediately after loading pages that render localized strings
Admin audit logs showing edits to language entries from unexpected accounts or source IP addresses
New or modified cookies, redirects, or injected DOM elements present on pages that reference language resources

Detection Strategies

Review the Quick.cms language storage (files or database tables backing the languages editor) for HTML tags or JavaScript constructs that should not exist in translation strings
Compare current language entries against a known-good baseline captured immediately after installation or last patch
Enable web server access logging for /admin requests to the language editor and alert on POST requests containing script-related tokens

Monitoring Recommendations

Monitor administrative session activity for anomalous edits to localization or language resources
Deploy a Content Security Policy (CSP) in report-only mode to surface script execution originating from unexpected inline sources
Alert on administrator account logins from new geographies or user agents that precede language-editor modifications

How to Mitigate CVE-2025-10018

Immediate Actions Required

Restrict access to the Quick.cms admin panel using network-level controls, such as IP allowlisting or VPN-only access
Audit all administrator accounts and remove or demote accounts that do not require language-editing privileges
Inspect current language entries for injected HTML or JavaScript and restore clean values from backup where tampering is found
Rotate administrator credentials and invalidate active admin sessions following any discovered compromise

Patch Information

No vendor patch or fixed version has been published at the time of writing. The vendor was notified early in the disclosure process but did not respond with vulnerability details or a vulnerable version range. Monitor the OpenSolution CMS Quick product page and the CERT.pl advisory for updates.

Workarounds

Enforce a strict Content Security Policy that disallows inline scripts and restricts script sources to known origins
Limit administrative accounts and apply multi-factor authentication to all admin logins
Place the application behind a web application firewall (WAF) with rules that block script and event-handler payloads in admin editor requests
Periodically export and diff language resources against a trusted baseline to detect unauthorized modification

bash

# Example CSP header to mitigate stored XSS execution
# Add to web server configuration (Apache / Nginx) serving Quick.cms
Content-Security-Policy: default-src 'self'; script-src 'self'; object-src 'none'; base-uri 'self'; frame-ancestors 'self'